1. Field of the Invention
The present invention relates to a winding method and apparatus for a toroidal coil.
2. Description of the Related Art
In a toroidal coil, a wire W is helically wound on a ring-shape core CR as shown in FIG. 15. To wind the wire W on such a coil, it is necessary to alternate a process for inserting the wire W into the center hole CR1 of the core CR and a process for bringing the wire W, which has passed through the central hole CR1, back to the entrance side of the center hole CR1 in such a way that the wire W moves around the core CR. It is also necessary to keep tensioning the wire W during winding, to fix the wire W on the core CR and minimize the diameter of the coil. Japanese non-examined patent publication JP63-034912 discloses a method of mechanizing such winding processes as shown in FIGS. 16A through 16E.
In this method shown in FIG. 16A, a rod-shape jig J is attached to the tip of the wire W. A feed chuck A holds the end of the jig J. The feed chuck A moves toward the core CR so that the jig J inserts into the center hole CR1 of the core CR. A driving chuck B holds the tip of the jig J which passes through the center hole CR1.
At this time, a roller R1 is placed on the exit side of the center hole CR1. The roller R1 is hereinafter referred to as the first roller R1. Next, the jig J is released from the feed chuck A and is pulled out from the center hole CR1 by the driving chuck B as shown in FIG. 16B. The jig J then returns to the entrance side of the center hole CR1 such that the wire W is wound around the first roller R1 as shown by an arrow Ya, reaching the condition shown in FIG. 16C. Here, the end of the wire W is fixed near the core CR by an appropriate holding chuck D. After the jig J returns, the feed chuck A holds the end of the jig J and the driving chuck B moves over to the exit side of the center hole CR1. Then, as shown in FIG. 16D, the first roller R1 moves away from the core CR and swivels around the core CR as shown by an arrow Yb while tensioning the wire W. Here, some parts of the feed chuck A and the driving chuck B are omitted in FIG. 16D.
When the first roller R1 moves over to the opposite side of the core CR, the wire W is wound around the core CR as shown in FIG. 16E. At this time, a roller R2 (hereinafter referred to as the second roller R2) different from the first roller R1 is placed on the exit side of the center hole CR1. After the first roller R1 swivels up to the position illustrated in FIG. 16E, the feed chuck A moves toward the core CR and then the driving chuck B holds the tip of the jig J which has passed through the center hole CR1. In this manner, the condition shown in FIG. 16A is again reached. From then on, the wire W is wound by repeating the above-mentioned steps while alternating the rollers R1 and R2. After each round of the wire W winding, the core CR rotates on its own axis by the prescribed angle (the angle corresponding to one pitch of the helical coil wound on the core CR).
The above-mentioned winding method requires following complicated operations. The first roller R1 and the second roller R2 must be capable of interchanging their positions, and of moving separately in the axial direction of the core CR (the axial direction of the center hole CR1). Also, after the first round of the wire W winding (after returning to the condition in FIG. 16A for the first time), when the roller R1 (R2) on the exit side of the center hole CR1 of the core CR moves away from the core CR to tension wire W, the roller R2 (R1) on the entrance side of CR1 is also wound by wire W. Thus, this roller R2 (R1) on the entrance side must move toward the core CR synchronously with the motion of the roller R1 (R2) on the opposite side. Therefore, it is desirable to develop a winding apparatus which performs the above-described operations using simple mechanisms.
Also, the above-mentioned winding method has the following drawbacks. As shown in FIGS. 16C and 16D, the jig J which has passed through the center hole CR1, moves over to the entrance side of the center hole CR1 by operating the driving chuck B and is re-gripped by the feed chuck A. Then, the rollers R1 and R2 swivel. In this procedure, without the jig J, the wire W is pulled toward the exit side of the center hole CR1 when the tip of the wire W returns to the entrance side of the center hole CR1 by operating the driving chuck B. Thus, the wire W is bent over toward the exit side of the center hole CR1 at the holding position of the driving chuck B, and cannot be held by the feed chuck A. Therefore, the jig J is indispensable to secure the straight part which is necessary for the re-gripping. In addition, as shown by X in FIG. 16D, the wire W bends at the end of the jig J when the rollers R1 and R2 start swiveling after the jig J returns to the entrance side of the center hole CR1. Therefore, the wire W is likely to be deformed, and cut during repeated windings.